Discharging sewage to a borehole

With the Environment agency clamping down on discharges direct to groundwater, it is becoming harder and harder to discharge to a borehole. This article explains the steps that a housing developer must go through if this is the only method of "getting rid" of wastewater.

Why is it so hard to gain a permit for borehole discharges?

Because the risk to groundwater contamination is significant.

Do other deep infiltration structures have the same restrictions in place?

Yes, any well, or deep structure that does not offer any filtration (concrete rings for example) will be met with the same stringent regulation.

What other options for sewage discharge could be explored?

There are many options that are within general binding rules and should be explored, prior to considering this as an option.

1. Take the waste to a public sewer.
2. Install a drainage field
3. Install a drainage mound (basically a drainage field higher in the ground, or slightly above ground)
4. Take the water to a ditch (even if it is a dry surface water ditch, although this will require a permit).

These options must be thoroughly and exhaustively explored and evidenced before considering a well, borehole or other deep structure.

When in the planning stage should sewage discharge be considered?

As early as possible. Why? because in the event a housing development cannot meet the general binding rules, a permit needs to be applied for which can take 9 months to 1 year. It is too late to decide that a site does not meet the regulations at the time of physically putting in the drainage system.

What to do if there is no other way of releasing treated sewage?

Given the Environment agency's approach to groundwater protection is strict (and rightfully so). If you have explored, and evidence all other possible options, Treatment of the water using a treatment plant is the first line of defence, however, in my opinion it is not enough to just treat the waste water using a package treatment plant.

Why is a treatment plant not enough?

if we read the Environment agencies approach to groundwater protection (page 25, section G9), we see that they state:

There are sufficient mitigating factors or measures to compensate for the increased risk arising from the
use of deep structures

A treatment plant does provide significant treatment to the wastewater. However, in my opinion, this is not enough. Why?: Because treatment plants can break, home owners can occasionally be unaware their system isn't working, bacteria in the system can die and therefore there is still risk of pollution to the groundwater.

What can be done to increase reduce the risk of pollution?

As stated in the previous paragraph, a treatment plant will provide good treatment to the water. But to really reduce risk of pollution, a tertiary filter should be added after the treatment plant. a trickle filter system would work well and would help to replace the protection a drainage field is offering.

Providing secondary treatment via a treatment plant then tertiary treatment from an energy free trickle filter system will not only significantly improve the water quality entering the ground, this method will also act as a back up in the event of power failure or breakdown of the treatment plant.

As an alternative, a reed bed of sand filter could be designed and installed after a treatment plant.

This doesn't guarantee that you will be allowed to discharge via a borehole, but it does, in my opinion offer the greatest protection to groundwater.

Important note:

It is very important to note that you must get the permit prior to installing the borehole, and the solution of a treatment plant and tertiary treatment system does not guarantee you will be granted a permit.

If you require a treatment plant/tertiary filter package for your site, feel free to contact me